HF RL Explorer

Provide a way to lookup chart instance given canvas element

Provide a way to lookup chart instance given canvas element: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). ChartJS already adds a $chartjs property onto the HTMLCanvasElement once instantiated, so it would make sense to add the instance to that property.

The task

ChartJS already adds a `$chartjs` property onto the `HTMLCanvasElement` once instantiated, so it would make sense to add the instance to that property.

Part of FineEnvs/MiMo-V2.6-RL-harbor-code.